Measuring Implosion Dynamics through ρR Evolution in Inertial-Confinement Fusion Experiments

The areal density (ρR) of D³He filled plastic capsules imploded at OMEGA has been measured at shock coalescence (1.7 ns) and, 400 ps later, during compressive burn, through the energy downshift of 14.7-MeV D³He protons. In this time interval, the azimuthally averaged ρR changes from 13±2.5 to 70±8 mg/cm². The experiments demonstrate that fuel-shell mix is absent in the central regions at shock coalescence, and that the shell has no holes during compressive burn. We conjecture that ρR asymmetries measured during compressive burn may be seeded by the time of shock coalescence.